Photographic gelatins

ABSTRACT

PHOTOGRAPHIC MATERIAL HAVING A GELATIN-SILVER HALIDE EMULSION LAYER OF WHICH THE GELATIN CONTAINING CATALASE OF MORE THAN 10 INTERNATIONAL ACTIVITY UNITS PER GRAM.

United States Patent 3,600,182 PHOTOGRAPHIC GELATINS Reinhard Matejec and Rudolf Meyer, Leverkusen, and Bruno Miicke, Cologne-Buchheim, Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany No Drawing. Filed Oct. 9, 1968, Ser. No. 766,317 Int. Cl. G03c 1/04 U.S. Cl. 96114.7 2 Claims ABSTRACT OF THE DISCLOSURE Photographic material having a gelatin-silver halide emulsion layer of which the gelatin containing catalase of more than international activity units per gram.

The invention concerns photographic gelatins with improved photographic properties, in particular with an improved stabilization of silver images contained therein, i.e., of latent images from developable silver nuclei as well as of visible images of metallic silver.

Gelatin is still the most important binder for silver halide emulsion coatings, though many attempts have been made to replace this binder with other synthetic substances. Gelatin, being a natural product, represents, as one of its disadvantages, a limited reproducibility in its production. Depending on raw materials and manufacturing processes used, the gelatin produced has different prop erties, and only a mixture of different gelatins makes it possible to obtain a product suitable for the production of photographic coatings with more or less uniform properties. Compared with this, synthetic binders offer the advantage that they can be produced with far more uniform properties. On the other hand, it was not possible heretofore to produce synthetic binders which, as to their photographic properties, could be compared to natural gelatin. The advantage of gelatin in this respect is its sensitivity increasing effect on the light sensitivity of silver halides. This effect is usually ascribed to the presence of sulphur compounds as ripening agents, which considerably increase the sensitivity of silver halide grains. Furthermore, gelatin can stabilize metallic silver, in particular latent silver images against the oxidative effect of atmospheric oxygen.

Though, as pointed above, gelatin is an excellent binder for light sensitive photographic coatings, it is desirable to further improve gelatins, in particular to provide a more uniform production of photographically highly active gelatin types.

The purpose of the invention is to develop gelatins for photographic silver halide coatings with improved properties.

It has been found that the photographic properties of gelatin considerably improve the stabilizing effect on latent images of silver nuclei and in visible images, and that, depending on its use, these properties can be brought to the desired level by adding catalase to the silver halide emulsion coating.

Gelatins made according to the invention, have a catalase activity of more than 10 international effectiveness units, preferably between 10 and 100 effectiveness units/ gram.

By definition, an international effectiveness unit is the quantity of catalase which, within one minute at 25 C., decomposes one micromol of H O i.e., which develops, within one minute, from an H 0 solution 1.12 10 cm. of O (p=1atm.).

Such gelatin types stabilize extraordinarily the latent ice image. Furthermore, the finished silver image becomes considerably more stable as to density and tone.

The catalase is added to the photographic emulsion at any time, preferably after chemical ripening. The same effect can be obtained if a finished silver halide emulsion coating is bathed in an aqueous catalase solution. Furthermore, it is possible to add the desired quantity of catalase to the gelatin prior to its use in the production of photographic material.

Generally, the catalase is used in form of an aqueous solution, buffered in respect of pH value. Such solutions are the usual form of catalase for use. They contain between 10 and 10 effectiveness units of catalase per liter. They can be produced according to known methods, such as that of K. G. Stern, Hoppe Seylers Zeitschrift fiir Physiologische Chemie (Journal for Physiological Chemistry), vol. 212 (1932), p. 207. Furthermore, commercial catalase preparations of bacterial origin can be used for this purpose. The catalase concentration, which can be varied within certain limits, according to the photographic requirements, can easily be determined through simple tests.

Catalase can be used in any desired silver halide emulsion. Silver chloride, silver bromide or mixtures thereof can be used as silver halides, possibly with a slight content of silver iodide up to 10 mol. percent.

The emulsions can also contain chemical sensitizers, for instance reducing agents such as stannous halides, polyamines such as di-ethylene triamine, sulphur compounds as described in U.S. Pat. No. 1,574,944. For purposes of chemical sensitization, the indicated emulsions can also contain salts of noble metals, such as ruthenium, rhodium, palladium, iridium, platinum or gold salts as described in the article by R. Koslowsky, Z. Wiss. Phot., vol. 46, pp. 6572 (1951).

The emulsions can also contain poly-alkylene oxides, in particular polyethylene oxides and derivatives thereof, as chemical sensitizers.

The emulsions made according to the invention can contain the usual stabilizers, such as homopolar or saltlike compounds of mercury with aromatic or heterocyclic rings, e.g., mercaptotriazole, simple mercury salts, sulfonium mercury double salts and other mercury compounds. Other stabilizers are azaindenes, preferably tetraor pentazaindenes, in particular those substituted by hydroxyl or amino groups. Such compounds are described in the article of Birr, Z. Wiss. Phot., vol. 47, pp. 2-58 (1952). Furthermore, heterocyclic mercapto compounds, such as phenyl mercaptotetrazol, quaternary benzothiazole derivatives, benzotriazole and similar substances can be used as stabilizers.

The emulsions can be hardened in the usual way, for instance with formaldehyde or aldehydes substituted with halogen which contain a carboxyl group, such as mucobromic acid, diketones, methane sulfonic acid esters, dialdehydes and other similar compounds.

EXAMPLE 1 A highly sensitive silver bromide-gelatin emulsion, containing approximately 6 mol. percent silver iodide, is spread on a cellulose triacetate film base. For photographic coating, the usual photographic gelatin is used.

The film sample thus prepared is divided into two parts. One series of strips is bathed for about 2 minutes in a 1% solution of technical catalase. The other series remains without treatment for purposes of comparison.

Both series are exposed in a conventional sensitometer for 10 seconds behind a grey step wedge, and then subjected for varying periods storage at 25 C. and 60% relative humidity.

After this, the strips are developed with the following developer composition:

The usual fixing, washing and drying then follow.

The stabilizing effect on the developed latent image in the material with catalase-containing gelatin is shown in the following density chart:

CHART 1 Developed Developed Developed immediately after 8 after 28 afterwards days days Wedge Sample Sample Sample step Conbathed Conbathed Conbathed in No. trol in catalase trol in catalase trol catalase EXAMPLE 2 Using an ordinary photographic gelatin, a AgCl/ AgBr-mixed grain gelatin emulsion is produced containing approximately 20 mol. percent AgCl and 20 mol. percent AgBr. After chemical ripening with thiosulfate, the emulsion is divided into two parts. One part is mixed with com. of a 0.1% catalase solution per liter emulsion, the other part being used as a control for comparison. Each of the two emulsions is then coated on barytacoated paper as the emulsion carrier.

The emulsions thus produced are exposed, as in Example 1, in a sensitometer for 10* seconds behind a grey step wedge and then subjected for varying periods to a 25 C. and 60 C. relative humidity atmosphere.

After this, the materials are developed with the following developer composition for 2 minutes at 20 C.:

G. p-Methylaminophenol 2 Hydroquinone 4 Sodium sulfite 25 Sodium carbonate 18.5 Potassium bromide 2 followed by the usual fixing, washing and drying steps.

The following density chart shows the stabilizing effect of the added catalase:

4 EXAMPLE 3 A highly sensitive AgCl/AgBr gelatin emulsion is coated on a coated paper as the emulsion carrier. The emulsion is covered with a protective gelatin surface coating of 1.5 1. thickness. Before coating, ml. of a 1% catalase solution is added to 1 kg. of coating solution for the protective surface coating (1.8% aqueous gelatin solution). In a parallel experiment, the same emulsion is coated with a protective surface coating containing no catalase.

The material is exposed and developed as indicated in Example 2. Three sensitometer strips (approximately 4 cm. wide) of the materials to be compared are placed in desiccator, on the bottom of which a container with 50 ml. of a 5% hydrogen peroxide solution is placed.

In the material without catalase, a change occurs in the color of the silver image due to the influence of the H 0 vapor, from neutral black to yellow-brown after 12 hours, and to red-brown after 24 hours. The change in the color is first visible in the wedge steps having a lower silver image density. The silver image of the test emulsion containing catalase in the protective surface coating shows no change of color and remains neutral black.

We claim:

1. Gelatin associated with silver halide in a photographic light-sensitive composition, said gelatin containing catalase in amounts of more than 10 International Effectiveness Units per gram.

2. The gelatin according to claim 1 wherein said catalase is present in amounts ranging from 10 to International Effectiveness Units per gram.

References Cited UNITED STATES PATENTS 2,965,484 12/1960 Tulagin et al. 9619X FOREIGN PATENTS 811,907 4/1959 Great Britain 96-94 1,115,625 5/1968 Great Britain 96114.5

OTHER REFERENCES Hamm, F. A. et al., The Electron Microscopy of Photographic Grains, Specimen Preparation Techniques and Applications, Journal of Applied Physics, vol. 24, No. 12, December 1953, pp. 1495-1502.

WILLIAM D. MARTIN, Primary Examiner M. R. LUSIGNAN, Assistant Examiner US. Cl. X.R. 

